The preparation of polyether polyols by oxyalkylation of an alkylene oxide with a low molecular weight starter compound in the presence of a double metal cyanide (DMC) catalyst is known. Polyether polyols produced by DMC catalysis are often characterized by low unsaturation and low polydispersity (i.e. a narrow molecular weight range), which is particularly desirable in many applications for such polyether polyols, such as in the manufacture of flexible polyurethane foams.
Continuous processes for preparing such polyether polyols using DMC catalysts are also known. In some cases, for example, a continuous stirred tank reactor (“CSTR”) is used in which the CSTR is initially charged with a mixture of starter compound and DMC catalyst, the catalyst is activated and additional starter, alkylene oxide and DMC catalyst are continuously added to the CSTR and polyether polyol is continuously removed from the CSTR.
The foregoing oxyalkylation in the presence of a DMC catalyst is an exothermic reaction. As a result, continuous processes for preparing polyether polyols using DMC catalyst, such as those that use a CSTR, can be limited in rate by the heat removal rate of the reactor or heat exchangers in the system. This can limit the capacity of plants that incorporate such processes.
As a result, it would be desirable to provide systems and processes for the production of polyether polyols using DMC catalysis in which the energy created by the exothermic oxyalkylation reaction is efficiently removed from the reactor and is put to beneficial use, while also allowing significantly increased space-time yields, thereby increasing plant capacity, and causing no changes in product quality.
The present invention was made in view of the foregoing.